全新java初学者实践教程6(Java SE5.0版)
x0A7O 基本语法3
u`_*g^5q" pISp*& G(/DtY] 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
%D`o yS!(Ap [font="Times] 1.循环语句[font="Times]:while,do-while,for
8O7Yv< =xL )$DTg) [font="Times]2.分支语句[font="Times]:if-else,switch,
?'eq",c#4N [font="Times]
/aY pIMi9} 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
s9O2k}] [font="Times]
>zs5s 4.异常处理语句[font="Times]:try-catch-finally,throw
jAC78n,Fi@ d]SYP 实践:
Q =#I9- [font="Times] 1.循环语句
9pLg+6O [font="Times] while 语句
~jN'J+_$ [font="Times]class While {
eh(<m8I [font="Times]public static void main(String args[]) {
sZg6@s= [font="Times]int n = 10;
<uci9- eC [font="Times]while(n > 0) {
&w85[zs [font="Times]System.out.println("tick " + n);
D//=m= [font="Times]n--;
!:3.D, [font="Times]}
+&5'uAe [font="Times]}
}Cj8 [font="Times]}
d(;4`kd*N [font="Times] do…while 语句
D."=k{r. [font="Times] class DoWhile {
%d2!\x%bG [font="Times]public static void main(String args[]) {
I[d]!YI}F [font="Times]int n = 10;
I4=Xb^Ux [font="Times]do {
=rFN1M/n{E [font="Times]System.out.println("tick " + n);
=lp1Z> [font="Times]n--;
eg<pa'Hw [font="Times]} while(n > 0);
Zb_apjg[4 [font="Times]}
y9 L14 [font="Times]}
`s"d]/85VW 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
O=}g4c [font="Times] for语句
XRtD< jlA" [font="Times] class ForTick {
'wQv3; [font="Times]public static void main(String args[]) {
Fky?\ec [font="Times]int n;
D-&an@ [font="Times]for(n=10; n>0; n--)
]s_8A`vm [font="Times]System.out.println("tick " + n);
H'DVwnn>ik [font="Times]}
,<`)>2 'o [font="Times]}
)OP){/ 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
8e&p\%1 还有啊,[font="Times]for循环的部分可以为空的
S,{tV=&m] [font="Times]class ForVar {
]Oeh=gq [font="Times]public static void main(String args[]) {
@Jn!0Y1_3 [font="Times]int i;
7TX2&kMoc [font="Times]boolean done = false;
xZ .!d.rn [font="Times]i = 0;
np9dM [font="Times]for( ; !done; ) {
MYdO jcN [font="Times]System.out.println("i is " + i);
`<frgXu64 [font="Times]if(i == 10) done = true;
[f/I2 [font="Times]i++;
-c*\o3) [font="Times]}
swcd&~9r [font="Times]}
>IfV\w32 [font="Times]}
循环语句的例子下载 f&KdlpxKv [font="Times] 2.分支语句[font="Times]
~h$wH{-U# [font="Times] if/else语句
-ijC_`> [font="Times]class IfElse {
6'vbT~S! [font="Times]public static void main(String args[]) {
.;
Q:p* [font="Times]int month = 4; // April
`3 cCH [font="Times]String season;
uLR<FpM [font="Times]if(month == 12 || month == 1 || month == 2)
vB'>[jvA| [font="Times]season = "Winter";
6 %Mt [font="Times]else if(month == 3 || month == 4 || month == 5)
12UD19! [font="Times]season = "Spring";
Cu;5RSr2Z [font="Times]else if(month == 6 || month == 7 || month == 8)
v,@F|c?_S [font="Times]season = "Summer";
?-)I+EAnE [font="Times]else if(month == 9 || month == 10 || month == 11)
Na{Y}0=^y [font="Times]season = "Autumn";
L2UsqVU [font="Times]else
1q7tiMvV- [font="Times]season = "Bogus Month";
}baR5v [font="Times]System.out.println("April is in the " + season + ".");
UL$}{2N,_ [font="Times]}
j<<3Pr [font="Times]}
`G9 l [font="Times]//这段程序输出[font="Times]:
5GzFoy)j> [font="Times]//April is in the Spring.
3FE( }G [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
soRv1) el [font="Times] switch语句
yx38g
ca [font="Times] class Switch {
zeb=8Dg
: [font="Times]public static void main(String args[]) {
tq1CwzRX [font="Times]int month = 4;
> L2HET [font="Times]String season;
_}xd}QW [font="Times]switch (month) {
I:cg}JZ>| [font="Times]case 12:
i1lBto[ [font="Times]case 1:
S$,'Q^~K [font="Times]case 2:
u\yVR$pQ [font="Times]season = "Winter";
w;6bD'.>; [font="Times]break;
Lh.b5Q| [font="Times]case 3:
"R>FqX6FB [font="Times]case 4:
4GdX/6C. [font="Times]case 5:
58Xzup_" [font="Times]season = "Spring";
e'%v1-&sP [font="Times]break;
"qz3u`[o [font="Times]case 6:
rwLAW"0Qz [font="Times]case 7:
B;>{0
s [font="Times]case 8:
K<`osdp=& [font="Times]season = "Summer";
`F YjQe"p [font="Times]break;
=@&cH Y [font="Times]case 9:
s$ENFp7P [font="Times]case 10:
EOj"V'! [font="Times]case 11:
b?X.U}62_ [font="Times]season = "Autumn";
l e4?jQQ@L [font="Times]break;
+ZMls
[ [font="Times]default:
@mP]*$00 [font="Times]season = "Bogus Month";
RGKYW>$0RR [font="Times]}
)Z 9E=% [font="Times]System.out.println("April is in the " + season + ".");
8Me:Yp_Xt [font="Times]}
PXzsj. [font="Times]}
分支语句代码下载 |1b_*G4| yZr M.%V [font="Times]switch语句适合于条件非常多的逻辑
IYn]U4P.
请看上述语句可以混合使用,请看
下载例子